I am a non US citizen and it's bean a while that I have subscribed to compeete on an artificial inteligence competition, however when I was reading the wiki I found that to claim the price a non Us tax payer have to fill a Form W-8BEN,

However in this form they were asking to fill an SSN or ITIN also a foreign tax identifier.

Is it required to fill those two identifiers? if so how can a non US citizen to get those identifiers? is there any specific procedure to do that?